众所周知，鳃是鱼类进行气体交换的呼吸器官，尤如高等动物的肺脏一样，是生命活动的要害部门。鳃的组织构造纤细而脆弱，且因直接与外界环境接触，故极容易受各种病原体如细菌、霉菌及寄生虫等的侵害。有些病原体通过血液循环而引起全身性败血病；有些进入于其它亲和性内脏器 It is well-known that gills are respiratory organs of fish for gas exchange, as the lungs of higher animals are vital components of life activity. Gill tissue structure is delicate and fragile, and because of direct contact with the external environment, it is extremely vulnerable to various pathogens such as bacteria, molds and parasites and other violations. Some pathogens cause systemic septicemia through blood circulation; some enter other affinity visceral organs